An important object of communication is to enable anyone to communicate or exchange intentions or information when necessary at any place at any time. Accordingly, mobile communication service, in addition to conventional fixed communication service for communication between fixed points, has been developed. Mobile communication service enables communication between mobile objects, such as ships, automobiles and aircraft, and between mobile objects and general subscribers or offices. Recently, portable telephone sets and cordless telephone sets for mobile communication have actively been developed.
Generally, in using a telephone set, the telephone receiver is held to the ear and the telephone transmitter is held near the mouth. Accordingly, a sufficiently large distance must be secured between the telephone receiver and the telephone transmitter of a telephone set, even if it is a portable telephone set. Therefore, conventional telephone sets are long and large.
A folding portable telephone set provided with a folding cover for protecting the switching unit has been proposed. In this previously proposed portable telephone set, the transmitter is provided on the folding cover, and the receiver is provided on the casing so that a sufficient distance is secured between the transmitter and the receiver.
As mentioned above, the telephone receiver and the telephone transmitter of the conventional portable telephone set are spaced a distance substantially equal to the distance between the ear and the mouth. Therefore it has been difficult to construct the portable telephone set in a satisfactorily small size. Techniques of manufacturing the component parts of portable telephone sets have made remarkable progress in recent years and small, inexpensive component parts are available. From the view point of component parts, it is comparatively easy to miniaturize portable telephone sets. However, an ergonomic requirement that a distance corresponding to that between the ear and the mouth of a man must be secured between the telephone receiver and the telephone transmitter is a principal problem in miniaturizing a telephone set.